The SB diet is one of the least restrictive low carb diets out there, however it still does have a lot of restrictions, and it's usually those restrictions that cause so many people to jump ship after 2 or 3 weeks. So you're not alone.
The thing to remember is that a lifestyle change should not come from a diet. It should come from the way you look at yourself first, and see what changes you would like to make all-around. The SB has a lot of good info and can be used as an inspiration or catalyst to get you going, but not the do-all for a lifestyle change.
The bottom line is that decreased caloric intake and increased daily exercise is the most sensible and sustainable strategy.
BTW, check out episode 15 of this weeks podcast about diets. It should be out on 12/16/05: